Volume 2 wind energy 2 01 – wind energy – introduction

Volume 2 wind energy 2 01 – wind energy – introduction Volume 2 wind energy 2 01 – wind energy – introduction Volume 2 wind energy 2 01 – wind energy – introduction Volume 2 wind energy 2 01 – wind energy – introduction Volume 2 wind energy 2 01 – wind energy – introduction Volume 2 wind energy 2 01 – wind energy – introduction Volume 2 wind energy 2 01 – wind energy – introduction Volume 2 wind energy 2 01 – wind energy – introduction

2.01 Wind Energy – Introduction JK Kaldellis, Technological Education Institute of Piraeus, Athens, Greece © 2012 Elsevier Ltd All rights reserved 2.01.1 Introduction 2.01.2 Pros and Cons of Wind Energy 2.01.3 Brief Content Presentation 2.01.4 Conclusions References Further Reading Relevant Websites Glossary Aeolus According to Greek mythology, Aeolus was the ruler of winds Calm spell The period of time during which wind speed takes values lower than a predefined value Normally calm spells are considered to occur when the appearing wind speed is lower than ms−1, although in the case of wind turbines, calm spells may be considered as corresponding to the periods that wind speed is lower than the wind speed required for the machine to start operating Capacity factor The capacity factor of a wind turbine refers to the ratio of actual energy production of the machine for a given time period to the respective potential energy production of the same machine if it had operated at its rated power for the entire time period Energy pay-back period The period of time required for the entire amount of energy embedded in a system (during its life span) to be compensated by the system's energy production Feed-in tariff Feed in tariff refers to a policy mechanism developed for the support of renewable energy technologies, through the award of a certain payment per kWh for electricity produced by a renewable resource and fed into the grid Feed in tariffs may vary on the basis of technology, geographical location and installation site Life-cycle Life-cycle refers to the period of time capturing all stages involved in a project, including energy projects as well Regarding an energy plant (e.g., a wind farm), lifecycle concerns the stages of equipment manufacturing, transportation, installation, operation and decommissioning 10 10 Neural network The term actually refers to artificial neural networks composed by artificial interconnected neurons which are used to mimic properties of biological neurons, in order to solve artificial intelligence problems R&D The term is used to describe research and development, and refers to creative work undertaken on a systematic basis in order to increase the stock of knowledge, and the use of this stock of knowledge to devise new applications Technical availability Technical availability is configured by the hours of operation of a given wind turbine or a given wind farm, by subtracting the time period that the machine is kept out of operation due to, e.g., scheduled maintenance, unforeseen faults of the machine, etc Wind energy The kinetic energy carried by a wind stream of certain characteristics (e.g., wind speed and air density) Wind farm-wind park A group of wind turbines installed within the boundaries of a given area (either onshore or offshore) for the purpose of massive power generation Wind hybrid stand-alone system A power configuration that is used for the electrification of consumers that are not interconnected to an electricity grid and that combines two or more energy conversion systems – with one of them being a wind turbine (or a wind farm) – with an energy storage device Wind power The conversion of wind energy to useful forms of energy, i.e mechanical work Wind turbine A man-made machine used to exploit the kinetic energy of wind so as to produce wind power in the form of electricity 2.01.1 Introduction Ever since the early days of mankind, wind was viewed as one of the most arresting natural phenomena In fact, according to Greek mythology, humans worshipped the wind god Aeolus, who along with his eight assisting gods, that is, the so-called Anemoi, each assigned with one wind direction (Boreas (N), Kaikias (NE), Eurus (E), Apeliotes (SE), Notus (S), Livas (SW), Zephyrus (W), and Skiron (NW)) (Figure 1), was considered as the ruler of the winds, thus underlining the importance of wind energy for the economic and production activities during even this early historic period In this context, wind energy was initially exploited for the navigation of ships (Figure 2), while further, the first relatively simple applications of wind energy exploitation for the production of mechanical work appeared At the same time of course, in order for their constantly increasing needs to be satisfied, people had to exploit other energy sources as well However, despite the existence of alternative energy sources, wind machines were found to comprise a rather useful solution for the grinding of grains and other Comprehensive Renewable Energy, Volume doi:10.1016/B978-0-08-087872-0.00201-8 Wind Energy – Introduction Figure The tower of winds, situated in Athens (shown are Boreas and Skiron) Figure Greek stamp demonstrating the Argo sailing ship Figure Aspects of a medieval-type windmill for grinding grain and an American-type windmill used for water pumping production activities up until Medieval times [1], while a great number of multiblade wind machines installed mainly in the United States during the nineteenth century were used for water pumping purposes [2] (Figure 3) Although acknowledging the importance of these early stages of wind energy history, it is believed that true and actual interest in wind energy grew during and after the end of the two world wars and wind energy was established after the consecutive energy crises between 1970 and 1980 [3] More specifically, in the early 1980s, contemporary power generating wind turbines of 15–100 kW first Wind Energy – Introduction 250 m 180 m 150 m 125 m 110 m 15 m 1980 1985 50 m 40 m 20 m 1990 1995 2000 2005 2010 2015 2020 Figure Time evolution of contemporary wind turbine size Based on data from European Wind Energy Association (2009) Wind energy the facts, technology, wind turbine technology http://www.wind-energy-the-facts.org/en/factsheets.html (accessed September 2011) [4] appeared, followed by machines of somewhat greater power of around 300 kW Accordingly, up until the mid-1990s, the rated power of wind turbines was in the order of 600–1000 kW, while nowadays, the market of modern wind turbines is dominated by multimegawatt machines, with rotor diameters even exceeding 150 m (Figure 4) [4] In this context, current short-term realistic targets in terms of rated power are elevated to machines of 10 MW, destined mainly to serve offshore wind energy applications [5, 6], although future innovative concepts will increase machine capacity even more [7] As a result of these constant developments, the global installed capacity of wind turbines has nowadays exceeded 200 GW (Figure 5) [8], with the contribution of wind energy to the local electrical energy balance of certain countries even exceeding 10% (Figure 6) [9] At the same time, based on future plans and announcements made by the authorities of the most developed countries, wind energy applications are expected to develop even further, with a target of 1000 GW installed wind power to be achieved by 2030 (Figure 7) [10] Considering the situation encountered so far, efforts are undertaken in this introductory chapter of the encyclopedia in order to first present the most important pros and cons of wind energy and to then provide a short summary of the following 21 chapters comprising the wind energy volume 2.01.2 Pros and Cons of Wind Energy Wind energy, which is explicitly the exploitation of the kinetic energy of wind, has attracted the interest of people since the early days of history Note that the global wind potential is configured mainly by the absorbance of only a small proportion (∼0.2%) of the incident solar energy on the various regions of the planet, which eventually leads to the development of climate Time evolution of global wind power capacity 500 000 Forecast 450 000 Installed capacity (MW) 400 000 350 000 300 000 250 000 200 000 150 000 100 000 50 000 15 14 20 13 20 12 20 11 20 10 20 09 20 08 20 07 20 06 20 05 20 04 20 03 20 02 20 01 20 00 20 99 20 98 19 97 19 19 19 96 Year Figure Time evolution and prediction of global wind power installed capacity Based on data from Global Wind Energy Council (2011) Global wind report 2010 http://www.gwec.net (accessed September 2011) [8] 4 Wind Energy – Introduction Contribution of wind energy to the electricity generation of certain leading countries 20% Denmark Spain Germany Portugal Contribution share 16% 12% 8% 4% 0% 1994 1997 2000 2003 2006 2009 Year Figure Wind energy contribution in the electrical energy balance of representative countries Based on data from Energy Information Administration (2011) International energy statistics http://www.eia.gov/ (accessed September 2011) [9] Reference scenario of future regional wind energy development in 2020 and 2030 400 Installed capacity (GW) 350 2020 2030 300 250 200 150 100 50 OECD Pacific (incl South Korea) Africa Middle East China India Dev Asia (excl South Korea) Latin America North America Transition economies EU-27 Figure Regional development of wind energy according to the reference scenario of the Global Wind Energy Council Based on data from Global Wind Energy Council (2011) Global wind power outlook 2010 http://www.gwec.net (accessed September 2011) [10] In this context, wind energy comprises a nonfinite renewable energy source with a vast potential that is, however, only partly exploited by the currently available wind energy technology [11, 12] In parallel, it should also be noted that wind potential is distributed across the world, without of course neglecting the fact that in some areas, local wind potential may be of higher/lower quality Thus, as it may easily be concluded, the availability of wind energy throughout the planet contributes remarkably in providing balanced development opportunities all over the world [13], regardless of the existence of other fossil fuel reserves (e.g., oil, coal, natural gas, and uranium) distributed unevenly [14] Finally, given also the fact that wind energy is normally of higher quality in more remote and less inhabited/developed areas, efforts for exploiting the local wind potential contribute not only to the increase of energy independence but also to the support of distributed generation patterns [15, 16] and the electrification of isolated consumers [17, 18] On the other hand, apart from its expansion to the most remote areas, wind energy has recently entered the urban environment as well, with concepts of building integrated wind turbines aspiring to contribute remarkably to the future electrification of urban consumers [19–21] At the same time, given the severe environmental problems of our planet, exploitation of wind energy may be determined as an environmentally friendly way of covering energy needs, with minimum, local-character environmental impacts involved [22, 23] being at least two orders less severe than that caused by conventional energy sources such as nuclear, coal, and oil [24] In addition, Wind Energy – Introduction installation and operation of wind parks may be considered as of low risk, with accidents recorded being minimum, while additionally, the impacts of natural disasters (e.g., fires, floods, and earthquakes) are also not considerable in the inhabited surroundings of operating wind farms For this purpose, wind energy is established as a clean (green) energy source, which is also determined by a rather low energy payback period of less than year, reflecting the contribution of the respective technology to sustainable development as well [25, 26] On the other hand, wind energy is not always available, meaning that it is based on noncontrollable natural phenomena, which are responsible for the so-called intermittency of wind energy production [27] However, despite the stochastic nature of wind energy, there are numerous advanced calculation tools that can provide reliable prediction of wind speeds [28–31], although due to the fact that wind energy exploitation is limited within a specific range of wind speeds (usually between 3–4 and 25–30 m s−1), the possibility of long-term periods during which no energy production is encountered (i.e., either calm spells or extreme wind speeds) should also be considered As a result, when considering wind energy, it is imperative to also consider a reserve energy source such as backup conventional power stations, energy storage systems [32–36], and hybrid units [37–40], which can be used to complement any energy deficit caused by the intermittency of the primary wind energy system In addition, intense variation of the wind speed may also cause severe impacts on the quality of the electricity produced (e.g., voltage and frequency issues) [41–44], which requires installation of additional cost compensation mechanisms in order to provide consumers with the appropriate quality of electricity Finally, given the fact that the energy density of wind is relatively low, the per unit area maximum exploitation of wind energy by contemporary wind turbines ranges mainly between 150 and 300 W m−2 This fact along with the technological status of modern wind machines imposes the need to operate a significant number of large-scale wind turbines in order for sufficient energy production to be achieved For example, a modern wind turbine of MW has a rotor diameter of around 100 m and a swept area of around 8000 m2, while providing an annual energy production in the order of 7500 MWhe Furthermore, due to the considerable size of modern machines and the fact that they may operate in highly visible areas, the visual impact perception by the local inhabitants found in the proximity of a given wind farm suggests one of the major issues concerning wind energy [45, 46] Similarly, the issues of noise production and impacts on local ecosystems (mainly bird collision) caused by the operation of wind farms are also of major importance [47–49] In this context, it should be noted that although such issues should always be taken into account when considering installation and operation of a new wind farm, they usually influence relatively restricted areas in the surroundings of wind farms and are normally the subject of detailed and analytical studies carried out by wind energy developers [50, 51] Synopsizing, by considering the pros and cons of wind energy, which will be further analyzed and elaborated in the following chapters, it is the opinion of the current volume’s editorial team that wind energy suggests a renewable, widely distributed, and environmentally friendly energy source, applications of which are determined by high-quality technological standards and contribute considerably to the satisfaction of constantly increasing energy needs and the protection of the environment In this context, it is expected that the development rate of such applications shall persist at high levels encountered so far, aiming to contribute more than 15% to the planet’s electrical energy needs within the next 20 years 2.01.3 Brief Content Presentation Chapter 2.02 provides a thorough view of wind energy issues A review of the past and current energy status on a global level is first undertaken, analyzing in detail the major energy trends as well as the contribution of fossil fuels and renewable energy sources According to the existing official data, the current contribution of wind energy is rather limited, although increased wind energy participation should be expected in the future fuel mix of our planet In this context and through the determina­ tion of the current wind power status and the evaluation of long-term wind energy developments, predictions concerning future prospects of wind energy appear to be rather encouraging Thus, Chapter 2.02 clarifies the present role and future prospects of wind energy in the energy balance of the planet, giving at the same time a rather enlightening picture of the global energy market Accordingly, an overview of wind energy history starting from ancient windmills and extending to contemporary modern wind turbines is included in Chapter 2.03, with a scientific trip dating back 7000 years that is, to the use of sails to propel reed boats in Mesopotamia, being the basis of this analysis Subsequently, the most well-known windmills are described, while the basic ideas and concepts used are also mentioned Moreover, the major milestones in the progress of wind power applications and the history of the main relevant organizations are presented, while finally, the major competing wind turbine designs are briefly investigated, including the horizontal and vertical axis machines, the number of their blades (basically two- vs three-bladed ones), etc Chapter 2.04 is devoted to giving an overview of the methods used to estimate the wind energy potential, starting from resource description and resulting in contemporary methods of forecasting More precisely, the basic elements of wind potential evaluation theory and the main measurement techniques are demonstrated Also the most representative analytical and numerical models used to accurately describe the wind potential of an area are presented, while the most widespread software tools used in order to reproduce the wind resource atlas of an area are described The chapter concludes with a brief description of the most reliable wind potential forecasting methods, including artificial neural network models and Bayesian model averaging Besides, the main scope of the entire analysis is estimation of the expected wind energy yield of a wind park as well as scheduling of optimum wind energy integration into an electrical network and implementation of the necessary system maintenance 6 Wind Energy – Introduction The scope of Chapter 2.05 is to describe the transition from ancient windmills to modern electricity generating wind turbines, with special emphasis on underlining the significant changes that the wind energy conversion technology has undergone This is followed by a discussion of the basic principles governing the wind energy conversion process and a classification of wind turbines, with every wind machine being categorized according to its special characteristics (e.g., number of blades, axis orientation, and control type) Finally, the chapter concludes with an overview of the main components of established wind turbines, while additional effort has been placed on giving a brief description of the time evolution of commercial wind turbines In Chapter 2.06, a systematic study is carried out in order to present the main directions for the estimation of energy production by contemporary wind turbines For this purpose, wind potential principles with operational characteristics of contemporary wind turbines are combined in order to calculate the corresponding mean power coefficient and the corresponding capacity factor In this context, the basic theoretical models used to describe the wind turbine output and the available wind potential are analyzed Furthermore, specific issues such as the reliability of calculations based on real measurements compared with pure analytical equations, the impact of hub height on the corresponding energy yield, the wake effect, and the air density impact on the corresponding energy yield are all considered, while subsequently, the impact of the technical availability on the wind turbines’ energy yield is also examined Finally, the representative commercial wind turbines for various typical wind potential cases are classified, providing at the same time detailed guidelines on the selection of the most appropriate wind turbine for a given wind site, in order to ensure both maximum energy yield and optimum operation of the machine The contents of Chapter 2.07 include an overview of the basic principles applied during the design of a new wind park In this context, a general description of the issues that should be taken into consideration during the wind park design procedure is given, including site selection, wind potential evaluation, wind turbine micrositing, array losses, infrastructure required, collaboration with the local electrical network, social approval, and wind park output estimation Selected representative case studies are briefly analyzed, while special attention is given on presenting the basic installation issues of commercial wind turbines This chapter concludes with a brief presentation of some of the most characteristic wind parks in the world, including one of the biggest onshore (Roscoe, Texas) and offshore (Thanet, UK) installations Chapter 2.08 focuses on providing an overview of the basic aerodynamic methods used to analyze contemporary wind turbines, with regard to modeling and prediction of aerodynamic forces on the various parts of the machine, considering at the same time that wind turbine aerodynamics is the main discipline for the design and construction of wind turbine blades In this context, all concepts, starting from the basic one-dimensional momentum theory up to the contemporary three-dimensional methods using the complete Navier–Stokes equations, are briefly analyzed Accordingly, the status of the most important research areas within the aerodynamics of wind turbines, rotor wakes, and wind farms is presented, following which the optimization of wind turbine rotors with respect to minimizing the cost of energy produced by wind turbines is described Finally, an introduction to the prediction of aerodynamic noise from wind turbine rotors is also provided Chapter 2.09 provides an introduction to loads for both onshore and offshore wind turbines with a focus on the respective windand wave-induced ones, so as to assess the structural integrity and power performance of wind turbines Taking into consideration the significant activity and the prospects of offshore wind energy, emphasis is placed on offshore applications as well In this context, the basic types of loads along with their sources are presented, including loads in the operational and survival conditions, fault cases, controller actions, and response-induced forces Several innovative concepts concerning huge onshore and offshore turbines as well as floating turbines that require dynamic analysis and comprehensive load modeling are also examined, with selected case studies for both fixed and floating wind turbines being provided Chapter 2.10 gives an overview of the main electrical parts of contemporary wind turbines along with their basic operational principles More specifically, power control, generators, power electronics, grid connection, and lightning protection are all discussed in detail In this context, the analysis is focused on the basic types of electrical generators (synchronous and induction machines, constant-variable speed, etc.), yaw motors, and pitch control motors, while a brief presentation of the wind turbine ancillary electrical equipment is included as well Note that although the content of this chapter mainly concerns present-day multimegawatt turbines, small machines are also taken into account On top of that, a list of the most important manufacturers in the field is included and some insight into the future outlook of the sector is provided Chapter 2.11 investigates the control systems of contemporary wind turbines, including an overview of basic principles and representative types Besides, a brief presentation of the dynamic control theory is included, along with an introduction on monitoring and power production control systems In this context, the power production control comprises the generator torque control and the pitch control subsystems, the power electronics, and the grid connection On the other hand, yaw control is also discussed, while emphasis is placed on operating states and fault diagnosis, as well as on the fail-safe backup systems analysis Finally, the main sensor and actuator manufacturers of the field are briefly presented Chapter 2.12 mainly describes testing procedures of new wind turbines along with the up-to-now existing standardization processes Additionally, emphasis is placed on discussing the major safety issues as well as any manufacturing, installation, and operational issues related to the safe operation of wind turbines, designating coherence between these elements Accordingly, the various international standards (mostly the International Electrotechnical Commission) related to design aspects for large and small wind turbines onshore and offshore and testing of power performance, mechanical loads, acoustic noise, power quality, and safety are described, while the various certification schemes are also examined Finally, a presentation concerning the organizations involved in the formal testing, standardization, and certification procedures for both existing and new wind turbines and wind parks is included Wind Energy – Introduction Chapter 2.13 gives an overview of the most important issues related with the design and implementation of a wind power project Actually, in this chapter, all stages of the project development process, in terms of what needs to be done and how to it, are described in detail In this context, the main parameters affecting the design of a new wind park along with the basic practical steps of the implementation of such a project are examined, with emphasis on infrastructure considerations as well as on financial issues during the project design and implementation Subsequently, environmental aspects and social approval of new power stations are analyzed together with the experience from mitigating possible reactions in such projects Finally, available information concerning the operation and maintenance of wind parks is also provided, including condition and performance monitoring as well as plant decommissioning and site restoration Chapter 2.14 presents offshore wind energy activity all over the world, providing a historical review from the very beginning of offshore applications along with an overview and future trends of the technology employed In addition, the basic concepts of offshore wind farm design as well as issues concerning installation and maintenance activities are discussed Accordingly, special emphasis is placed on presenting the support structures and towers used in offshore wind parks, while finally the most important economic, environmental, and social considerations during the development and operation of offshore wind farms are examined in detail Chapter 2.15 reviews the generation costs concerning onshore and offshore wind parks, determines the relative importance of turbine prices, slight costs, and other factors, and indicates how generation costs are influenced by the major economic parameters (capital cost, inflation rate, etc.) and the depreciation period Accordingly, additional parameters that should be taken into consideration for a fair comparison between wind energy and fossil fuel electricity generation cost are also examined, for example, external cost, embedded benefits, and extra balancing cost, while methods of valuing wind energy are also considered Finally, examples of ‘total cost estimates’ are discussed, taking into account most of the debits and credits associated with wind energy applications The chapter concludes with a discussion of published forecasts of future price trends Chapter 2.16 deals with the main social and environmental benefits from the introduction of wind energy in a given area, such as reduction of carbon dioxide and air pollutants’ emissions, decrease in the import of fossil fuels, creation of new job positions, and regional development In addition, environmental concerns resulting from wind power plants, such as noise, visual impacts, and possible disturbance of the wildlife are described Accordingly, special attention is paid on offshore wind power plants since they may impose distinct and in many cases quite different environmental impacts from onshore installations Besides, another very interesting issue investigated is the social acceptance and public attitude of wind energy, while finally methods for the reliable assessment of impacts, mitigation measures, and future trends are also being discussed Chapter 2.17 examines the role of renewable energy within the context of global energy markets, investigating at the same time the skepticism toward wind energy In this context, the link between energy and economic development is considered, while special emphasis is placed on the role of fossil fuels and nuclear energy Accordingly, the opportunities of renewable energy sources and more specifically of wind energy to largely contribute to the world energy market are discussed, underlining that economic feasibility is the major obstacle for the wider participation of wind energy Subsequently, the economics of wind energy are investigated in view of the economic structure of electricity grids, while finally the costs that wind energy may impose on the rest of the electricity generation systems are also examined, especially in case of large-scale wind energy integration Chapter 2.18 presents an overview of the opportunities and problems associated with the integration of wind energy into electrical networks currently in operation or under development More precisely, a description of wind energy integration require­ ments and consequences that the particular characteristics of wind energy, namely its fair predictability (stochastic behavior) and fluctuations of generated power, may induce into an electrical network is provided Accordingly, distributed systems are presented and the benefits of wind energy integration into common interconnected microgrids and stand-alone microgrids are described This is followed by a discussion of wind forecasting and economic issues, considering also future trends concerning significant wind energy integration into existing electrical grids Chapter 2.19 introduces the reader to the definition and special features of wind-based stand-alone hybrid energy systems The introduction emphasizes on the basic characteristics of stand-alone and hybrid energy systems including also representative application examples in different sectors After a short reference to the historic development of wind-based stand-alone systems, the contribution of wind energy in distributed generation is analyzed The most common commercial system configurations of stand-alone installations are discussed in detail through various case study results in order for the reader to obtain a comprehensive view of the opportunities given by the different combinations Furthermore, a short description of the energy storage systems available is presented along with a short reference to the most well-known free software tools that are extensively used for the design and optimization of hybrid energy systems Chapter 2.20 gives an overview of the wind power industry in the course of time along with the corresponding market development, addressing at the same time key drivers and new trends In this context, the galloping wind power development noted during the past 15–20 years on a global scale is illustrated, emphasizing on the long-term annual growth rate of almost 25% Accordingly, the major wind energy markets are analyzed, including China, the United States, Germany, and Spain Finally, a brief presentation of the major wind power manufacturers along with their market share time evolution is included In Chapter 2.21, a systematic study is carried out in order to present the main trends, prospects, and R&D directions of wind turbine technology For this purpose, investigation of the main technological developments throughout the entire period of wind energy growth is undertaken, while emphasis is placed on recording the most important research efforts that have allowed wind energy establishment Accordingly, several research efforts remarkably financed during the previous years are acknowledged, Wind Energy – Introduction while simultaneously, major wind energy technological problems and the most challenging future R&D issues are discussed The chapter concludes by synopsizing the most important problems to be faced by the wind energy community at all levels in order to ensure that growth trends encountered until today will not be limited in the years to follow The volume is integrated in Chapter 2.22 with the examination of representative wind power applications In this context, one of the most important applications analyzed is the desalination of seawater and/or brackish water, utilized in order to supply the required quantities of freshwater to various areas of the planet facing water shortage Furthermore, other significant applications of wind energy, like the traditional and well-known application of wind-based water pumping and the more modern application of power generation in remote telecommunication stations, are also briefly discussed Additionally, emphasis is placed on the sizing procedure of these systems as well as on their financial viability Finally, selected examples of the most representative special wind power applications along with their main technical characteristics are demonstrated as well 2.01.4 Conclusions Considering its status quo at the global scale, wind power can nowadays be perceived as one of the most mature and reliable energy solutions, which is reflected by the constantly growing installed capacity, recently exceeding 200 GW On the other hand, although now suggesting an established power generation source, research efforts in the field of wind energy are still ongoing, with emphatic targets set at both the national and international level configuring the future prospects of wind power applications At the same time, we are now arguably facing development of the fourth-generation wind machines, while also noticing multidirectional shifts, for example, from onshore to offshore wind power applications, from large-scale rural wind farms to urban environment small-scale wind machines destined to serve on-site domestic electrical loads, and from centralized wind energy generation to distributed generation patterns involving wind-based stand-alone applications Within this constantly evolutionary environment in terms of technological trends, global wind power market facts also produce consecutive changes of scene In this context, according to the current situation, China is currently the leader in wind energy, operating a total of ∼45 GW of wind power within its territory, followed by the United States (∼40 GW), Germany (∼27 GW), and Spain (∼21 GW) Meanwhile, India with galloping rates of development during the recent years has installed a cumulative capacity of more than 13 GW Acknowledging the above, parallel development of different world regions noted reflects the relatively even distribution of wind resources across the globe, nowadays extended to also capture the offshore wind potential In this context, the developing rates of offshore applications are even more encouraging, with regional plans, such as those of the European Wind Energy Association, aiming at 600 TWhe produced by offshore wind energy by 2030 At the same time, according to the reference scenario of the Global Wind Energy Council, the total installed capacity of wind power applications (both offshore and onshore) by 2030 is expected to exceed 1000 GW, thus allowing for considerable contribution of wind energy to the global electrical energy consumption On the other hand, to achieve the ambitious targets concerning further promotion of wind energy into electricity markets, numerous challenges need to be encountered first, involving among others design and material issues, integration of wind energy into electrical grids, adaptation of wind energy into urban environments, development of more efficient and reliable small-scale wind turbines, and exploitation of deeper waters for offshore applications For this purpose, sufficient financial support in the R&D section of wind energy is thought to be imperative, especially if considering that innovative concepts in the field of wind power applications emerge continuously, introducing wind machines of even GW rated power At this point, it must be underlined that support offered to wind energy throughout this period of growth, either in the form of policy tools such as feed-in tariffs or in the form of considerable research funds, was efficiently used and has allowed wind energy technology to establish itself in the competitive environment of energy markets Furthermore, policy instruments developed to promote further penetration of wind energy were accordingly applied in other renewable energy source tech­ nologies, producing similar progressive results However, earlier development of wind energy in comparison with alternative energy sources has provided wind power technologies with a significant edge that may under certain conditions ensure an even more promising future for wind energy applications At the same time, constant cost reduction and increase of energy efficiency for modern wind turbines set the basis for further expansion of wind energy applications, now being in a position to favorably compete not only with other alternative energy source installations but also with conventional power generation (e.g., oil based and coal based) Considering also the efforts undertaken in the field of environmental performance so as to reduce/eliminate the already mild impacts in terms of affecting local ecosystems and ensuring sustainable use of energy resources on a life-cycle basis, environmental benefits deriving from the increase of wind energy contribution will become yet more pronounced, even in the case that externalities attributed to fossil-based power generation are not entirely considered In conclusion, emphasis must be placed on the fact that wind energy has long since comprised a mature and reliable power source that has established its role in the world energy scene On the other hand, it seems that following a long period of continuous development and vast progress concerning mainly the concept of onshore wind farms, the time has arrived for wind energy to take the next step and identify itself as one of the main energy suppliers worldwide For this to be achieved, however, challenges emerging in each of the new wind energy directions (e.g., offshore wind, small-scale wind, urban environment integration, distributed generation patterns, wind hybrid stand-alone systems, and giant wind turbines) need to be encountered on the basis of persisting research efforts, sufficient financial support, fostering policy initiatives, and public perception of the beneficial attributes of wind energy Wind Energy – Introduction References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26] [27] [28] [29] [30] [31] [32] [33] [34] [35] [36] [37] [38] [39] [40] [41] [42] [43] [44] [45] [46] [47] [48] [49] [50] [51] Pasqualetti MJ, Righter R, and Gipe P (2004) History of wind energy In: 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Heidelberg, Germany: Springer Mathew S and Philip GS (2011) Advances in Wind Energy Conversion Technology, 1st edn Berlin, Heidelberg, Germany; New York: Springer Gipe P (1995) Wind Energy Comes of Age, 1st edn New York: Wiley Kaldellis JK (2005) Wind Energy Management, 2nd edn Athens, Greece: Stamoulis Burton T, Sharpe D, Jenkins N, and Bossanyi E (2001) Wind Energy Handbook, 1st edn Chichester, UK: Wiley Nelson V (2009) Wind Energy Renewable Energy and the Environment, 1st edn Boca Raton, FL: CRC Press, Taylor & Francis Group Ackermann Th (2005) Wind Power in Power Systems, 1st edn Chichester, UK: Wiley Mathew S (2006) Wind Energy: Fundamentals, Resource Analysis and Economics, 1st edn Berlin, Heidelberg, Germany; New York: Springer Stankovicˇ S, Campbell N, and Harries A (2009) Urban Wind Energy, 1st edn London, UK: Earthscan Twidell J and Gaudiosi G (2009) Offshore Wind Power, 1st edn Brentwood; Essex, UK: Multi-Science Publications Wood D (2011) Small Wind Turbines Analysis, Design and Application, 1st edn Berlin, Heidelberg, Germany; New York: Springer Asmus P (2000) Reaping the Wind: How Mechanical Wizards, Visionaries, and Profiteers Helped Shape Our Energy Future, 1st edn Washington, DC: Island Press Relevant Websites http://www.eia.doe.gov – US Energy Information Administration http://www.gwec.net – Global Wind Energy Council http://www.ewea.org – European Wind Energy Association http://www.wind-energy-the-facts.org – Wind Energy the Facts (European Wind Energy Association and Intelligent Energy) http://www.ieawind.org – International Energy Agency – Wind Energy Systems http://ec.europa.eu/research/energy/eu/research/wind/support/index_en.htm – European Commission – Research and Innovation in Wind Energy http://ec.europa.eu/energy/renewables/wind_energy/wind_energy_en.htm – European Commission – Energy–Wind Energy http://windpower.sandia.gov – US Sandia National Laboratories – Wind Energy Department http://www.nrel.gov/wind – US National Renewable Energy Laboratory http://www.dewi.de – German Wind Energy Institute http://www.risoe.dk – Danish National Laboratory for Sustainable Energy ... (MW) 400 000 350 000 300 000 25 0 000 20 0 000 150 000 100 000 50 000 15 14 20 13 20 12 20 11 20 10 20 09 20 08 20 07 20 06 20 05 20 04 20 03 20 02 20 01 20 00 20 99 20 98 19 97 19 19 19 96 Year... attributes of wind energy Wind Energy – Introduction References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [ 12] [13] [14] [15] [16] [17] [18] [19] [20 ] [21 ] [22 ] [23 ] [24 ] [25 ] [26 ] [27 ] [28 ] [29 ]... 1 5–1 00 kW first Wind Energy – Introduction 25 0 m 180 m 150 m 125 m 110 m 15 m 1980 1985 50 m 40 m 20 m 1990 1995 20 00 20 05 20 10 20 15 20 20 Figure Time evolution of contemporary wind turbine size